©2003/04 Alessandro Bogliolo Computer systems A quick introduction

©2003/04 Alessandro Bogliolo Mother Board Hardware architecture System Bus Peripheral Bus Peripherals ScreenPrinterSpeakersNetworkKeyboardMouse Bridge Micro Processor RAM Output Input Storage DATA BUS ADDRESS BUS ROM Clock

©2003/04 Alessandro Bogliolo Software architecture BIOS OPERATING SYSTEM APPLICATION SOFTWARE Device drivers User interface USER HARDWARE

©2003/04 Alessandro Bogliolo Memory hierarchy L1 Cache RAM Virtual Memory L2 Cache 16Kbyte 64Kbyte 512Mbyte 2Gbyte size cost speed Microprocessor Mother board Hard disk distance from CPU CPU The memory hierarchy realizes a good trade-off between performance/cost and size, showing to the CPU the performance of the fastest cache and the size of largest virtual memory. Locality of memory accesses is exploited to bring at the higher memory levels the content of memory cells that are likely to be accessed by the CPU in the near future

©2003/04 Alessandro Bogliolo Mass memory Non-volatile memory devices: do not need power supply to keep stored data –Hard disk –CD Rom –Floppy disk –Flash memories Made available by the Operating System through device-specific drivers Explicitly used by applications and users to store programs and data

©2003/04 Alessandro Bogliolo File system File: coherent set of binary data stored in a non- volatile memory (a file may contain a sequence of instructions, a text, an image,...) File system: hierarchical organization of files made available by the Operating System to manage the storage space Each file has –a name: unique within the entire file system –a format: needed to interpret the content of the file –a size: the number of bits/bytes it contains –a place on a storage device

©2003/04 Alessandro Bogliolo File system C: ProgramsData PersonalWork Presentations Lesson1.ppt C:\Data\Work\Presentations\Lesson1.ppt Device name Path name File name Extension Directory (or folder): file containing a list of other files Full name

©2003/04 Alessandro Bogliolo Software description Programming language: formal language used to specify an algorithm to be executed by a computer Instruction set: set of the instructions directly interpreted and executed by a given CPU Low-level language: hardware-dependent language close to the instruction set of the target CPU High-level language: hardware-independent programming language that need to be automatically translated in order to be executed Source code: text file describing an algorithm in terms of a high-level proramming language Executable code: binary file containing the executable description of an algorithm Program: (set of) executable files implementing a given functionality

©2003/04 Alessandro Bogliolo Software life-cycle algorithm source codescript program input output Programming Compilation Execution Debugging Interpretation Execution Programming Debugging Development Usage Compiled programming language Interpreted programming language